The present invention relates to a portable information terminal such as a notebook-sized personal computer, and particularly to the terminal having a circuit for wireless communication to an outside.
Among personal computers (PC), a notebook-sized PC, which is portable and occupies a little space on a desk, has been widely used in these days. FIG. 5 is a lateral cross sectional view of a conventional notebook-sized PC. Lid 3 is mounted to the rear end of case 1 with hinge section 2 so that lid 3 can open until a certain angle with respect to case 1. A lock mechanism (not shown) prevents lid 3 from opening when the PC is hand carried.
Case 1 is made of metal, e.g., magnesium alloy, and formed by die-casting, or made of metal plate and formed by pressing. Thus, case 1 is conductive and shielded so that high-frequency components such as an inner clock will not leak to outside. A plurality of keys for inputting letters, numbers and marks are placed on case 1. On the rear part of case 1, input/output (I/O) terminal 5, e.g., a printer output terminal, is provided.
Inside of case 1, mother board 6, on which major circuits including CPU 7 of the PC are mounted, is placed. Lid 3 has liquid crystal display (LCD) 8 on the surface confronting an operator. Connecting wire 9 between mother board 6 and LCD 8 is located through hinge section 2.
In front of mother board 6, radio circuit board 10 is mounted in case 1 for communicating to an outside, e.g., a cellular phone, personal-handy-phone, wireless local area network (LAN). An end of coaxial cable 14 is connected to an antenna terminal of radio circuit board 10. Coaxial cable 14 is located in case 1 and connected to external antenna-connection-terminal 17, which is disposed at the rear section of case 1. Coaxial cable 18 from terminal 17 is located in hinge section 2 and lid 3, i.e., behind LCD 8, thereby connecting to antenna 19 which rises to the highest when lid 3 opens.
In such a conventional notebook-sized PC shown in FIG. 5, since the rear section of case 1 is crowded with I/O terminal 5 such as a printer-output-terminal and connecting wires 9 to LCD 8, mother board 6 mounting major circuits of the PC is generally placed at a rear part of case 1. Thus radio circuit board 10 of a wireless communication device is obliged to locate at a front part of case 1.
Antenna 19 is disposed at the rear section of case 1, i.e., away from a human body, in order to avoid lowering sensitivity, and is coupled to a wireless communication device with coaxial cables 14, 18. Coaxial cables 14, 18 are located across case 1 from the wireless communication device disposed at the front section to antenna terminal 17 for outside as well as antenna 19 disposed at the rear section of case 1.
Coaxial cable 14 is located near CPU 7 mounted on mother board 6. A low level high-frequency signal is induced at antenna 19 and supplied to the input terminal of the antenna of radio circuit board 10 via coaxial cables 18, 14. According to this positional relation, a clock signal of CPU 7 interferes with this low level high-frequency signal and lowers its S/N ratio.
A portable information terminal having wireless communication device comprises the following elements:
A conductive case;
A radio circuit board having an antenna terminal and being placed at a front section in the case;
An external antenna terminal or an antenna placed at a rear section of the case;
A cable-leading-out hole disposed at the front section of the case;
A cable-leading-in hole disposed at the rear section of the case;
A cable-groove recessed from the surface into inside of the case, the groove running between the cable-leading-out hole and the cable-leading-in hole;
A coaxial cable connecting the antenna terminal to the external antenna terminal or the antenna; and
A lid for covering the cable-leading-out hole, the cable-leading-in hole and the cable groove.
The coaxial cable connects the antenna terminal on the radio circuit board to the external antenna terminal or the antenna through the cable-leading-out hole, cable groove, and cable-leading-in hole. The coaxial cable is free from interference with other circuits in the case, in particular with the clock in a CPU on a mother board, so that the information terminal can receive a radio signal at a high S/N ratio.